On Wed, May 07, 2025 at 03:26:08PM +0300, Anton Gavriliuk wrote: > > `iostat -dxm 5` output during the fio run on both kernels will give us some indication of the differences in IO patterns, queue depths, etc. > > iostat files attached. Yeah, that definitely looks like MD is the bottleneck. In both traces the NVMe drives are completing read IOs in about 110-120us. In fedora 42, the nvme drives are not at 100% utilisation so the md device is not feeding them fast enough. That can also be seen in that the rocky 9.5 kernel with a nvme device queue depth of about 4 IOs, whilst it is only 1.5 for the fedora 42 kernel. Given that nobody from the block/MD side of things has responded with any ideas yet, you might just have to bisect it to find out where things went wrong... -Dave. -- Dave Chinner david@xxxxxxxxxxxxx
